The Intercontinental, stuck on the city's edge and secured behind checkpoints on a hill, had been hit before, in 2011. Indeed, its vulnerability meant Western officials often stayed clear, as they do of many major hotels.

In a testament to how badly the security situation in Kabul has deteriorated, the State Department suggested in its warning last week that the Hotel Baron -- a massively fortified complex for Western contractors near the airport -- might even have been a target. Nowhere is really safe now.

Smoke billows from the Intercontinental Hotel after the attack.

The mantra from the NATOcoalition mission is that 2018 is meant to be the year the Afghan government starts regaining territory. The cycle of positive messaging has developed its own rhythm over the past 16 years, so that journalists and observers no longer need challenge every prediction. We will just have to wait and see what comes. It couldn't get much worse than it is now.

But what can we learn from this one, brutal episode of the war?

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First, the response time of the Afghan special forces appears to have been swift. Sadly they are well practiced at major events in the capital. That's comforting, but for the wrong reasons.

Second, much still remains unclear -- including exactly how many people died. Official figures say 18, but local media reports suggest it might be as many as 40.

A particularly unlucky Ukrainian air crew were caught up in the attack, among many other Afghans, who on a Saturday night would have been clambering for a moment of respite from the iron corridors of life in Kabul's barricaded streets. The slow emergence of information is a sign of how secrecy is beginning to dominate much of the conflict in Afghanistan. From US President Donald Trump's desire to not telegraph his punches to the enemy, to the Afghan government's decision to classify the injury and death tolls of their security forces, much of this war is now hidden behind a veil. The belief is that makes it easier to fight the enemy, but it also sadly makes it easier to hide things that didn't go as planned.

An Afghan security official stands guard as black smoke rises from the Intercontinental Hotel Sunday.

Third, there are three possible culprits, and that's not good news. The Taliban claimed the attack. But some Afghan officials have pointed the finger at the Haqqani network, aligned to the Taliban but based principally in Pakistan, enabling Kabul to point the finger at Islamabad for providing safe havens for militants. That is the same allegation leveled by the United States before Washington that froze millions in security aid to Pakistan.

The field of insurgent groups has become more crowded however since ISIS-K (ISIS Khorosan) turned up and sought to claim some of the more hideous attacks in Kabul. The fact that there are now three groups who could be to blame shows how the insurgency is metastasizing.

But finally, what we learn most clearly from this attack is that despite the clarity of the US warning and the fact there are only a handful of major hotels in Kabul that could have been the target, the attack couldn't be prevented. The freedom of movement around the capital enjoyed by this insurgency is such that the "ring of steel" that once kept NATO officials and Afghan families safe has all but melted away.